Abstract: The failure behaviors of thermal barrier coatings deposited on turbine blades were studied. The blades were divided into 9 areas and the microstructure and composition of coatings were investigated by scanning electron microscopy(SEM) and energy dispersive spectrometer(EDS). It was found that the trailing edge area presented the interfacial cracking of bond coating and substrate because of oxidation of bonding layer and the occurrence of a large amount of spinelle resulting from higher service temperature. However, the leading edge area presented the delamination of TGO/top coat interface. CMAS deposits were observed in all samples. CMAS adhered to the surface of the coating, and infiltrated into the interior of the coating along the longitudinal cracks and pores, which led to the delamination of the coating and exfoliation of the coating.